1. Field of the Invention
The present invention relates to a switch device that is used in various types of electronic devices including a timepiece such as a wristwatch, a cellular phone, and a portable information terminal, and a timepiece including the switch device.
2. Description of the Related Art
For example, a switch device for a wristwatch is known in which a tubular member is mounted in a through hole of a wristwatch case, an operation member is slidably provided in the tubular member with it protruding inside and outside the wristwatch case, and a waterproof ring is provided on the outer circumferential surface of the operation member, so that waterproof protection is achieved by the waterproof ring being slid while being in pressure contact with the inner circumferential surface of the tubular member, as disclosed in Japanese Patent Application Laid-Open (Kokai) Publication No. 2004-271361.
In this type of switch device, a ring attaching groove is provided in the outer circumferential surface of the operation member, and the waterproof ring is fitted in the ring attaching groove. In this state, the operation member is slidably inserted into the tubular member of the wristwatch case so that the outer circumferential portion of the waterproof ring comes in pressure contact with the inner circumferential surface of the tubular member, and the inner circumferential surface of the waterproof ring is pressed toward the inside of the ring attaching groove with the reactive force of the resultant contact pressure force, whereby waterproof protection is achieved.
However, in this switch device, when the waterproof ring in pressure contact with the inner circumferential surface of the tubular member slides along with the sliding operation of the operation member, the outer circumferential surface of the waterproof ring is worn by the friction of the waterproof ring with the inner circumferential surface of the tubular member. This wearing leads to a reduction in the pressure contact force of the waterproof ring, which results in a reduction in the waterproofness. Accordingly, it is difficult to ensure the reliability of the waterproofness over a long period of time.